A bran muffin for breakfast, salad for lunch and low-fat snacks in between. Sounds like a weight-loss plan that works! Not so fast – these and other so-called “diet” foods can be a big fat landmine. Learn how simple diet mistakes can boost calories and widen your waistline…

You're trying to lose weight, watching what you eat and choosing foods you think will help melt away that muffin top. But you've hit a weight-loss plateau.

Those “healthy” diet foods may be to blame.

“A lot of my patients hear someone on TV or the radio spouting the benefits of a food and they get on the bandwagon without knowing the details,” says Jill Weisenberger, M.S., R.D.N., Lifescript's nutritional expert.

That can spell big trouble for your waistline.

The first step in making smarter dietary choices is not to blame the food.

“What bothers me the most is, people forget food is inherently good for you,” Weisenberger says.

But even virtuous fare has calories that can add up quickly.

“A lot of times, people don't think portion control matters if a food is good for you,” she adds.

Rather, it’s how we consume those healthful foods that cause problems. We investigated 10 foods that are popular with dieters and discovered how simple oversights can pile on the calories – and pounds.

Are you making these same mistakes?

Diet Mistake #1: Gluten-Free Food
Few trends are bigger than the gluten-free tsunami. Sales of gluten-free products are expected to top $15.6 billion by 2016, according to some estimates. One-third of American adults say they're reducing or eliminating gluten, according to NPD Group, a market research firm.

As many as 27% of those avoiding gluten do so to lose weight, according to Mintel, another market research firm.

But less than 1% of the population has celiac disease, a condition in which a person can't tolerate gluten -- a protein found in wheat, rye and barley -- and must avoid it.

Unless you have celiac disease, “gluten is neither essential nor detrimental to the overall health of your diet,” says Lisa Cimperman, M.S., R.D., a clinical dietitian at University Hospitals Case Medical Center in Cleveland and Academy of Nutrition and Dietetics spokeswoman.

Many packaged gluten-free products are nothing more than highly processed junk food with just as many calories and as much fat, sugar and sodium as their conventional counterparts.

So there's a good chance you're paying a premium for food that won't help you lose weight (or eat more healthfully) anyway.

“If it's a brownie, it's still a brownie, even if it's gluten-free,” Weisenberger says.

Diet Mistake #2: 100-Calorie Snack Packs
A 100-calorie snack pack seems like a smart way to exercise portion control, doesn't it? Portions matter, of course, but so does the quality of what you eat.

Packaged, portioned snack packs make it easy to fall into the trap of counting calories rather than looking at where those calories come from, says celebrity dietitian Ashley Koff, R.D., who developed the AKA Personal Shopper List to help consumers make what she calls “qualitarian” choices.

The jury is still out on why this is so, but some experts suspect calorie-free, artificially sweetened diet drinks simply aren't satisfying.

“A lot of people have a diet soda in lieu of food,” Koff says. “But it doesn't satisfy your body's need for actual nutrients, so you overeat later.”

How to kick a diet soda habit? Focus on what you're really craving. Is it bubbles? Sip sparkling water. Sweetness? Add fresh fruit.

Do you think packaged enhanced water, such as Vitamin Water is a good alternative? Take a closer look. A 20-ounce Vitamin Water has 120 calories and a staggering 31 grams (almost 8 teaspoons) of added sugar.

Diet Mistake #4: Muffins
You know better than to eat an entire double chocolate muffin from Costco for breakfast. Its size alone is a clue to its enormous calorie count (in case you were wondering, this muffin has 690 calories, 38 grams of fat – 11 grams saturated – and 48 grams of sugar).

“Muffins are pretty much a cupcake without the frosting,” Weisenberger says. “They’re made with a lot of oil, sugar and white flour. And while they might have some nutritious items thrown in, they’re still essentially a cupcake.”

Starbucks' Carrot Cake Muffin with Pecans has 370 calories – not terrible, but it also has 20% of your saturated fat for the day, 26 grams of sugar (that's almost as much as a Snickers Bar) and only 2 grams of diet-friendly fiber.

Order instead the Hearty Blueberry Whole-Grain Oatmeal. It packs a satisfying 4 grams of fiber and 5 grams of protein into just 160 calories. That simple switch will save you 210 calories and 3.5 grams of saturated fat.

Diet Mistake #5: Smoothies
Whether for breakfast or a post-workout snack, smoothies are a popular choice. What better nourishment than a fresh fruit-filled drink, bursting with vitamins and minerals?

But many juice-bar smoothies are little better than a milkshake, Weisenberger says. And with all the extras – protein powder, nut butters, etc. – it's hard for a dieter to know how many calories that “healthy” treat really has.

A 16-ounce (small) Aloha Pineapple Smoothie from Jamba Juice has 310 calories and 67 grams sugar (that's more sugar than in an In-N-Out chocolate shake). Maybe that's because it's flavored with pineapple sherbet.

That's because “when that fat is taken out, typically more sugar or salt is added,” Cimperman says.

Consider peanut butter.

A 2-tablespoon serving of reduced-fat peanut butter has 187 calories, 12 grams of fat (3 grams saturated) and 3 grams of sugar. The same serving of regular peanut butter has 188 calories per serving, 16 grams fat and 2 grams sugar. If you choose a no-salt-added variety, you'll even save nearly 190 grams of sodium.

But low-fat or fat-free options, such as plain dairy products, can be a good choice. Choosing nonfat over whole milk saves you 60 calories and 8 grams of fat (5 grams of it saturated) per cup.

Be sure to compare nutrition labels to save calories without adding sugar and sodium.

Diet Mistake #7: Flavored Yogurt
Yogurt loses its nutritional appeal when it’s loaded with artificial sweeteners and other high-calorie mix-ins. So if your yogurt is flavored, double-check that label.

For example, a 6-ounce Yoplait Strawberry Thick & Creamy has 180 calories, 28 grams of sugar and no actual fruit (and, therefore, no fiber). It also comes with a cocktail of additives to enhance the flavor, color and consistency.

Make a DIY yogurt parfait instead. Start with a 7-ounce container of plain, low-fat Greek yogurt, then add half a cup of sliced strawberries and a sprinkling of nuts. That comes in at 210 calories, but it has just 12 grams of sugar (none of it added), plus 20 grams of protein and a couple of grams of fiber to help you stay satisfied.

Diet Mistake #9: Salads
“People think salads are great – and they can be,” Cimperman says. “But people don't realize how many calories salad dressing or other toppings add.”

A chicken Caesar salad at The Cheesecake Factory tips the scales at 1,510 calories, 16 grams of saturated fat and a heart-stopping 1,450 grams of sodium. Even the “small” version weighs in with 980 calories.

That’s because we’ve forgotten what the salad is all about – the green stuff. When choosing a salad, “’think vegetable,’” Weisenberger advises. “Watch out for high-calorie condiments like croutons and bacon and creamy salad dressing.”

But packaged, highly processed organic food can seem more virtuous than it is.

“Junk food is still junk food,” Weisenberger warns. "Just because it's an organic sandwich cookie, it's still basically an Oreo.”

Use the same strategy as you would with any packaged food: Read nutrition and ingredient labels. You may be surprised. A regular Oreo cookie comes in at 53 calories while an organic Country Choice Sandwich Creme cookie has 65.

What's Your Diet Downfall?
You already know if you're a junk food junkie or a sucker for bread and butter. You know if you've got a sweet tooth or a salty incisor. So why isn’t your diet working? Find out if you're unwittingly sabotaging your weight-loss plan and adding inches to your waistline with this diet quiz.